In the Intelligent Transportation System (ITS), various types of information related to transportation are obtained in a timely manner through vehicle to vehicle (V2V) communication, vehicle to infrastructure (V2I) communication, vehicle-to-pedestrian (V2P) communication, or vehicle-to-network (V2N) communication. These communication manners may be collectively referred to as vehicle-to-everything (V2X) communication. X is a collective term for vehicles, infrastructures, pedestrians, and networks.
When a V2X message is transmitted from one user equipment (UE) to another UE by using a Long Term Evolution (LTE) technology, the message needs to be transmitted through a packet data network (PDN) connection. As shown in FIG. 1, a typical PDN connection includes a radio bearer 11, an S1 bearer 12, and an S5/S8 bearer 13. The radio bearer 11 is a bearer between the UE and an evolved NodeB (eNB). The S1 bearer 12 is a bearer between the eNB and a serving gateway (SGW). The S5/S8 bearer 13 is a bearer between the SGW and a packet data network gateway (PGW).
In a conventional cell handover (Handover) process, because PGWs are centrally deployed, a PGW corresponding to the UE remains unchanged in the cell handover process. However, in V2X communication, because the PGW is deployed near the eNB in a form of a local gateway (LGW), the UE may further need to be handed over between different PGWs. Specifically, a cell handover process 22 and a PGW handover process 24 are mutually separate. Usually, the cell handover process 22 is first performed, and then the PGW handover process 24 is performed. As shown in FIG. 2, in the cell handover process 22 based on an X2 interface, after establishing a second radio bearer with UE, a target eNB sends a request message to an MME. After receiving the request message, the MME executes a modify session (Modify Session) procedure. In the modify session procedure, a first S1 bearer is changed to a second S1 bearer, and a first S5/S8 bearer between a source SGW and a source PGW is not changed. After the cell handover process 22 ends, due to a factor such as a tracking area update (TAU) procedure, the MME is further triggered to determine whether the UE needs to perform PGW handover. If the UE needs to perform PGW handover, the MME triggers the target eNB to release the second S1 bearer, and triggers the source SGW to release the first S5/S8 bearer. In addition, the MME further triggers the target eNB to establish a third S1 bearer, and triggers the target SGW to establish a second S5/S8 bearer. Then, the UE communicates with an application server in the Internet through the second radio bearer, the third S1 bearer, and the second S5/S8 bearer. Because the second S5/S8 bearer is established after the cell handover process, relatively long handover time needs to be consumed starting from a moment at which the UE performs cell handover to a moment at which the UE can communicate with the application server in the Internet, and consequently a performance requirement of V2X communication on a transmission latency cannot be met.